A pioneering boat-based survey was conducted in 2019, to gather baseline information regarding the presence, composition, relative abundance, and spatial distribution of deep-diving and off-shore cetaceans in the northern South China Sea (SCS). A total of 27 sightings comprising at least 8 cetacean species were recorded during the 13-day survey, including 5 deep-diving species (i.e. Risso's dolphin [Grampus griseus], short-finned pilot whale [Globicephala macrorhynchus], sperm whale [Physeter macrocephalus], Cuvier's beaked whale [Ziphius cavirostris], and an unidentified beaked whale [either the ginkgo-toothed beaked whale, Mesoplodon ginkgodens, or Deraniyagala's beaked whale, Mesoplodon hotaula]), as well as 3 off-shore dolphins (i.e. pantropical spotted dolphin [Stenella attenuate], striped dolphin [Stenella coeruleoalba], and Fraser's dolphin [Lagenodelphis hosei]). With the exception of pantropical spotted dolphins, all other species were sighted and recorded at sea in the northern SCS for the first time. The pantropical spotted dolphin was the most frequently sighted species, comprising 30% of the total sightings. Deep-diving cetaceans were mainly sighted in the northern Xisha Archipelago, whereas off-shore dolphins were distributed across the survey area. The pantropical spotted dolphin was observed in aggregations of more than 100 individuals and nearly all encountered species included calves; these findings suggested that the survey area functions as an important feeding and calving ground for various cetacean species. This pioneering survey provides fundamental information regarding cetacean fauna in the northern SCS and highlights the need to strengthen research and conservation efforts concerning these species.

中文翻译：

---

对南海北部深潜和近海鲸类的开创性调查

2019 年开展了一项开创性的船基调查，以收集有关南海北部 (SCS) 深潜和近海鲸类动物的存在、组成、相对丰度和空间分布的基线信息。在为期 13 天的调查中，共记录了 27 次目击事件，包括至少 8 种鲸目动物，包括 5 种深潜物种（即 Risso 海豚 [ Grampus griseus ]、短鳍领航鲸 [ Globicephala macrorhynchus ]、抹香鲸 [ Physeter macrocephalus] ]、居维叶的喙鲸 [ Ziphius cavirostris ] 和身份不明的喙鲸 [ 银杏齿喙鲸、Mesoplodon ginkgodens或 Deraniyagala 的喙鲸，Mesoplodon hotaula ])，以及 3 只近海海豚（即泛热带斑点海豚 [ Stenella attenuate ]、条纹海豚 [ Stenella coeruleoalba ] 和弗雷泽海豚 [ Lagenodelphis horsei]）。除泛热带斑纹海豚外，所有其他物种都是首次在南海北部海域被发现和记录。泛热带斑纹海豚是最常见的物种，占总目击者的 30%。深潜鲸类主要分布在西沙群岛北部，而近海海豚则分布在整个调查区。在超过 100 只个体的聚集中观察到泛热带斑纹海豚，几乎所有遇到的物种都包括小牛；这些调查结果表明，调查区是各种鲸类物种的重要觅食和产犊场。